Control device for vehicle suspension



March 22, 1960 N. B. CHRISTENSEN 2, 29, 20

CONTROL DEVICE FOR VEHICLE SUSPENSION 2 Sheets-Sheet 1 Filed Feb. 13,1956 I W INVENTOR. 43 7; L By NORMANaCI-IRLSRNSEN 39 38 39 WQY/KQLM/ 42ATTORNEY United States Patent Ofiice 2,929,620 CONTROL DEVICE FORVEHICLE SUSPENSION Norman B. Ehristensem-North Olmsted, Ohio IApplication February 13, 1956, Serial No. 565,113 6 Claims; (Cl.267-'-'-65) This invention relates generally to suspension systems forvehicles. More particularly, the invention relates to pneumaticsuspension systems and provides means Where-' by pneumatic devices, suchas bellows type air springs,

may be made to respond to increased or decreasedvek hicle loads causinga substantial'changein the riding level of the vehicle, and yetpreventunnecessary alteration-of the riding level when the vehicle roadgearpasses-over a bump or drops into a hole, which actionsonlymomentarily alter the load on the suspension'system.

Pneumatic suspension systems, incorporating air springs interposedbetween the vehicle'frarne and road or runninggear, have-been slow toachieve commercialsuccess: be-

causethey have not been provided with'satisfactory valve means forcontrolling and regulating theair cushion with in the air springs.Maintaining a constant average air spring length or air cushion undervariable static load conditions, will-provide a constant riding levelfor the vehicle.

A- satisfactory valve means for efiectively controlling the riding levelof a vehiclehaving an'air-springsusped sion, must be responsive'tochanging static load conditions. An increase in theload will compressthe air spring. To restore the air spring to itsinitial position,-

air under increased pressure must be admitted into the air spring. Adecrease in load Will cause the air springto extend or raise,and-therefore, air must be exhausted or vented from within the airspring to restore it to its= initial position.

In addition to controlling the-supply and exhaust of air;

to and from an air spring, a satisfactory valve controlmeans-must'embody therein an adjustable time delay so that momentaryalteration of the static load on the suspension system, such as would beencountered duringnormal axle movement due to road irregularities, willnot cause-the valve to supply or exhaust air. This time delay feature isoften referred to as damping andpreferably is adjustable-over a timerange of from 1m 20 seconds,

as determinedby the weight of the vehicle, road condiof temperature,humidity and exposure tosand, dirt,-

grease, oil and water. I

It is therefore an objectof this invention to provide'an improvedpneumatic suspension system for vehicles, which system includes improvedvalve and valve control means for controlling. and regulating airsprings interposed between the vehicle frame and' roadgear, so astofurnish a constant ridinglevel for the vehicles anda constant averageair spring length.

Another object -isto provide animproved valve and controlnieansforcontrol'aiid regulation of a vehicleairspring suspension, whichcontrols the supply and exhaust 2,929,620 Patented Man: 22, 1960 2 ofair to the air springs, has a noveltime delay or damping feature, andis'operative under extremes of temperature, humidity and otherenvironmental conditions;

A further object is to'provide an improved valve and: control meanslocated remotely of the air springs and embodying therein a noveladjustable time delay or damping component to prevent excessiveoperation of thevalve; which is accurately responsive to persistentchanges' in' vehicle loading, and which isof simple, relatively uncomplex construction.

Afurther object is to providea novel time delay or. damping mechanismfor use with an air spring control valve.

, These and other objects will be appa'rent-in-view of-th'ef followingdetailed description'of'the inventioncorisidered" with the attacheddrawings:

In the drawings: 7

Fig. 1 is avertical sectional view through a vehi'cle' axle showing inelevation aportion of the vehicle. equipped with apneumatic suspensionsystem accordingi to the invention;

Fig. 2 is a side elevation-of a valve and'control means according to theinvention;

Fig. 3 is an endview ofthe valve'and control means;

Fig. 4 isa sectional view', taken substantiallyon line'i 49-4 of Fig. 3,showingthe'valve and control'means in the normal position;

Fig. 5 is aview, similar toFig. 4, showing thevalve? and control meansin an-air supplying position;

Fig. 6 is a'sectionalview, with somepa'rt's'showniii: elevation, takensubstantially on line66 of Fig. 2;With the view being rotatedapproximately and Fig. 7 is an enlarged fragmentary view of one of thepistons,

In the present invention'a-ride control valve meansfin dicate-dgenerally by the numeral 10;includesahousing 11, generally rectangularin cross section, which carrie s? a damping means, and an air supply andexhaust control means. The housing 11 islocated remotely andlaterally ofa conventional air spring-{bellows 12, ofmulti-ply rub ber and-cordconstruction and-havingone or more-con volutions 13. The upper end ofthe air spring is her nietically fastened by a-suita-ble clamp ring- 14tothe underside of a horizontaltransverse'member 1'5 consti tuting aportion of the vehicle frame. The member" 15 is securely affixed ateither end to longitudinalframe members 16'. The lower end of the airspring 12 is alsb hermetically fastened by a similar clamp-ring14to-the'*- upperside of a-bracket 17' on-the axlehousing lsof' thevehicle road gear. One mode of in't'eiposing an air'sprin'g between avehicle frame androad gear has-been' shown and described it will beunderstood, howeven-that the principles of the invention'are applicableto air springs interposed in other ways between the frame and road gear.Also, only one air spring has been'shown in con nection with thisinvention, butit'will be understood that the invention may be utilizedwith as many' air springs as are required on a vehicle;

A stub flange 20 which may be-locat'e'd atop. the-vehicledifierentialhousing 21, has a bolt 22 therethrough; which bolt extendsthrough an elongatedlcngitudinal slot 235 formed in thelowerend-ofacontrol valve-actuating rod' 24,'so'that rod 24 is slidablymounted'on bolt'22. The upper end'of the actuating-rod is fixedtoon'e-end of a control valve actuating shaft 25 and'secured thereon anut 26,- said-shaft being mounted for rotation in housing ll in amanner'to be described The'hou'sing' 11-pr'e'fei ably is locatedabove'and to" the rear of the horizontal planeof the axle,and'isfastened by' bolts 27; thatextend through openings=28 in thehousing, to'oneof the longi tudina-lframe members 16% Air, from a sourceunder pressure (not shown), is

3 supplied to the control device by suitable piping 32 having aconventional check valve (not shown) therein so that air cannot backout. The control device is connected by suitable piping 33 to an airspring fitting 34, which extends through the frame member into theinterior of the air spring. The piping 33 is the conduit for supplyingair to and exhausting air from the air spring 12, through the controldevice 10, as referred to later.

Referring to Figs. 4, 5 and 6, the housing 11 is provided with asubstantially central, vertical bore 35 that extends through thehousing, is tightly closed at the top with a plate 36 and bolts-37, andat the bottom with plate 38 and bolts 39. The bore 35 preferably issubstantially square in shape, and adjacent its bottom, a pair ofhorizontal'circular bores 40 and 41 communicate with bore 35 onoppositeside's thereof.

At the bottom'of housing 11, near one end thereof, is

an exhaust port 42 which vents air from the air spring 12 to theatmosphere through selected passages in the housing, as will be laterdescribed. Threaded into the outer end of the bore 40:is an air supplyfitting 43, to which the piping-32 is adapted to be tightly secured.Threaded into the outer end of bore 41, adjacent the exhaust bore 42 andcommunicating therewith interiorly of the housing, as described later,is a two-way fitting 44 to which the piping 33 leading to the bellows isadapted to be tightly secured.

; Inwardlyof air supply fitting 43, bore 40 has mounted therein, a valvering 45 having an outwardly extending hub portion 46 that fits snuglywithin the shank portion of fitting 43, and which carries an O-ring 47at its outer periphery to provide a fluid tight seal. Next to ring 45 1san outer circular plate 48 of less diameter than the diameter of bore 40so as to provide an annular space or passageway 49 around plate 48. Thefront face of plate 48 is provided with a groove or passage 50 extendingthereacross and communicating with space 49. Plate 48 has an inwardlyextending hub portion 51 that is apertured with the plate to slidablyreceive a piston rod, to be referred to later. Next to plate 48 is asupporting plate 52 that has an apertured hub portion 53 surrounding hub51 of plate 48 to support the latter and slidably receive said pistonrod. A small O-ring 54 is placed at the end of hub 53 to provide a fluidtight seal. Next to plate 52 is a ring 55 that engages a shoulder 56 inbore 40 and carries an O-ring 57 at its outer periphery to provide afluid tight seal. All of the foregoing elements in bore 40 are properlyheld in place by tightening fitting 43.

. Inwardly of the two way fitting 44, bore 4 1 has mounted therein avalve ring 60, similar to ring 45, having an outwardly extended hubportion 61 that is spaced from the shank portion 62 of fitting 44 toprovide a permanent space or passageway 63. As shown, space 63 isobtained by utilizing a relatively wide spacing ring 64 between fittmg44 and ring 60, the inner periphery of ring 64 being spaced from the hub61 of ring and the shank 62 of fitting 44, so that anannular passage 65is provided in communication with space 63. Ring 64 is also providedwith an annular groove 66 in its outer periphery, and a plurality ofradial passages 67 lead from groove 66 to passage 65. O-rings 68 and 69are carried at the outer peripheries of rings 60 and 64, respectively,to provide fluid tight seals. Next to ring 60 is a circular plate 70,similar to plate 48, of less diameter than the. diameter of bore 41, soas to provide an annular space or passageway 71 around plate 70. Theouter face of plate is provided with a groove 72 extending thereacrossand communicating with space 71. Plate 70 also has an inwardly extendinghub portion 73 that is apertured with the plate to slidably receive asecond piston rod, to be referred to later. Next to plate 70 is asupporting plate '74, corresponding to plate 52, that has an aperturedhub portion 75 surrounding hub 73 of plate 70 to support the latter andslidably receive said second piston rod. v A

small O-ring 76 is also placed at the end of hub 73 to provide a fluidtight seal. Next to plate 74 is a ring 77, similar to ring 55, thatengages a shoulder 78 in bore 41 and carries an O-ring 79 at its outerperiphery to provide a fluid tight seal. All of the foregoing elementsin bore 41 are properly held in place by tightening fitting 44.

The air supply fitting 43 has a short passage 80 that communicates witha horizontal valve chamber 81 in valve ring 45, and the latter chamberis connected by a small orifice or passage 82 with passage 50 in plate48. As previously explained, passage 50 communicates with annularpassage 49, which also communicates with a short lateral passage 83(Fig. 6) that leads to one end of anelongated passageway 84 extendingtransversely of the housing, and which is formed in a lateral extension85 of housing 11 (Figs. 3 and 6). The other end of passageway 84communicates with another short lateral passage 86 that leads to annularpassage 66. The latter passage is connected by radial passages 67 withannular passage 65 which also connects with passageway 63.- Fitting 44has a short passage 87 that communicates with passageway 63 and leads tothe piping connected to the air spring. The foregoing indicates the pathof any air under pressure admitted through supply fitting 43.

To control the passage of air under pressure through fitting 43, a valve88 is seated at the inner end of valve chamber 81, normally closingorifice 82. Valve 88 is in the form of a flat, reinforced, airimpermeable disc, and a small coil spring 89 in chamber 81 bearingagainst the valve has a normal bias tending to keep valve 88 seatedValve 88 is adapted to be unseated, to permit air under pressure to passthrough the device 10 to the air spring,

by the action of a piston rod 90 having a reduced outer end portion 91that is movable through orifice 82 to engage and unseat the valve underconditions to be described. Piston rod 90 is movable horizontally and isguided in its movement by plate hubs 5'1 and 53 through which it passes.Rod .90 has an enlarged head 92 on its inner end and carries a piston,indicated in its entirety by the numeral 93, which is movablehorizontally in bore 40.

Piston 93 comprises a rear plate 94 contacting head 92, a molded rubbercup 95, preferably formed of neoprene or other suitable material whichwill not deteriorate in oil, secured to plate 94. The sides of cup 95slidably engage bore 40 and are held in position against the bore by apreformed copper cup 96, the side of which engages bore 40 and iscorrugated to provide a plurality of horizontal passages'97 between thecorrugations, for a purpose to be described. A coil spring 98 isarranged between the bottom of cup 96 and plate 52, and this springtends to hold the piston cups in proper position and to urge the pistonand rod toward the right, as seen in Figs. 4and 5. e

Coming now to the passages which permit air to be exhausted from the airspring through'the exhaust port 42, the latter opens through a shortpassage 100 in housing 11 into annular passage 71 in here 41, whichpassage connects with passage 72. Valve ring 60 has a small orifice orpassage 101 that connects passage 72 with a valve chamber 102, similarto chamber 81, that leads to passage 63, which in turn leads to passage87 with which the air spring piping 33 is connected. A spring pressedvalve 103, identical with valve 88, is mounted in valve chamber 102 andnormally seats against orifice 191 to prevent the passage from the airspring.

The means for unseating the valve 103 under conditions to be described,to permit air to exhaust from the air spring, constitutes a piston rod90' and piston 93 similar in all respects to the piston rod 90 andpiston 93 previously described. Hence, to avoid repetition, the samenumerals, but primed, will be used to identify the various parts of thesecond piston rod and piston, and it will be understood that theelements indicated with primed numerals are identical with theirunprimed counterparts.

sage 105 that leads to a valve chamber 106, which is connected to bore35 by ahorizontal passage 107. Mounted-in chamber 106 is a needle valve108 adjustably mounted in housing 11 so as to vary and control theamount of liquid passing the valve from chamber 106 to passage 107 andvice versa;

Leading upward from bore 41' is another liquid carrying passage 105'that connects with a valve chamber 106, which is connected by ahorizontal passage 107' with bore-35. Mounted in chamber 106 is a secondneedle valve 108', also adjustably mounted in housing 11 so as tovaryand control the amount of liquid passing valve I08 from chamber 106' to'passage 107' and vice versa.

The-bore 35 is completely filled'iwith a suitable liquid such ashydraulic brake fluid; which also fills, passages 10.7 and 107', valvechambers 106 and 106', and passages I05 and 105. Also the areas betweenpiston cups 96 and 96, and supporting plates 52 and 74, respectively,are filled with this liquid; As described later, move= mento'f eitherpiston outwardly produces an inward move-' ment of the other piston,with consequent movement of the piston rods.

Movement of the pistons and piston rods is initially' accomplishedbyoscillatingmechanism actuated by shaft ZS'L As: shown, shaft issuitably'journaled for limited rotation in the upper part of housing 11and extends through bore 35. Both ends of shaft 25 are round so' as totum in its bearings, but'within the housing, theshaft generallysemi-circular in section, having a flattened lowersurface 25A.

Within the bore is a plunger cup 110, having a closed upper end 111which contacts shaft25 and is normally (as shown in Fig. 4) held againstthe flattened surface: 25A. Placed within cup 110 so as to contact theinner surface of the cup end 111, is a coiled, compression,

shaftfollower spring 112, the lower end of which extends below'the openend of the plunger cup, into engagement end ofwhich is in the samehorizontal plane as the lower surfaces of bores 40 and 41.

lh'h'orizontal alignment with the piston heads 92 and 92, extension 116receives a threaded horizontal plug.

117 that is adjustably mounted in the extension so that the outer faceof the plug engages the piston head 92' at the same. time that pistonhead 92 is in engagement with the adjacent surface of extension 116,substantially as indicated in Fig. 4. As soon as plug 117 is properlyadjusted, a locking, screw 118 that extends upwardly through the lowerend of extension 116 is tightened against the threads of the plug tolockthe latter in position. Thus, as the lower end of cup 114 turns leftor right, as the case may be, in response to turning movement of shaft25, one of the pistons is moved horizontally by the extension 116 or theplug 117, and the other piston follows in the same direction, by virtueof the action of the springs 98 and 98', and the liquid in the unit.

The operation of the device is as follows:

Let us assume that the normal static load on the vehicle suspension,which in this case is preferably a bus or truck, requires the airsprings to be inflated to a pressure of about p.s.i., in which conditionthe valves 88 and 103 are in the position shown in Fig. 4, that is,seated against the orifices 82 and 101 and preventing air from passingthrough the chambers 81 and 102.

Now assume that the static load is increased, for example,.by addingmerchandise or passengers. to the ve-. hicle. As the load is increased,the upper frame members 1'5 and 16move downwardly towardtli'e hous= ing-18, causing the air spring 12' to contract. this downward movement ofthe upper frame members, the control device 10 also moves downwardlycausingthe actuating shaft 25-to be turned by the actuating rod 24, thelower end of which is slidably attached to the differential housing, topermit sliding movement of the rod as the device moves downwardly.

As viewed in Fig. 1, an increased load would' cause the shaft 25 to turnin a clockwise direction to supply; air under pressure to the air spring12. Referring to Fig. 5, as shaft 25 is turned clockwise on its axis,the plunger cup 110 will be displaced downwardly within" the followercup 114, compressing" further thespring 112. As the spring 112 iscompressed, energy stored therein becomes directed substantiallyequally"between the upper end 111 of the plunger cup and the lower end 113 ofthe follower. The plunger end is fixed by theshaft and cannot bedisplaced upwardly, though it will immediately move upwardly in theevent shaft 25- is turned back even a small degree in acounter-clockwise" direction. As the spring 112 is compressed, thefollower cup 114 will be caused to turn on the same axis as shaft 25 toassume the position shown in Fig. 5. As the fol-' lower cup turns, theside of extension 116 will contact piston head 92 and move piston 93to'the left in'bore 40.

As described elsewhere, the space between piston cup" 96 and plate 52 isliquid filled. As piston 93 moves to" the left, for example, from itsFig. 4 position to its Fig. 5 position, liquid is forced over the frontedge of piston cup 96' and into the spaces 97 of said cup, along whichspaces it travels to the right in Fig. 5 to vertical passage 105.through the needle valvecontrolled passages to pas sage 105 and thenceto the space between piston cup 96 and plate 74. The speed of horizontalmovement of piston 93 to the left in Fig. 5 is determined and con"-'trolled by the position of the needle valve 108.

As piston 93 moves to the left in Fig. 5, so does pis ton rod with itsreduced end 91,, causing valve 88 to be unseated and permittingadditional'air to pass into valve chamber 81, and then through thevarious pas sages to the air spring 12'. This additional air must beunder a greater pressure than the air already in the air spring 12, andwill extend the air spring to its initial position.

As the air spring extends, the upper framemembers' 15 and 16 moveupwardly from the axle housing'18 causing shaft 25 to be turned by theactuating rod' 24 a counter-clockwise direction as viewed in Fig. 5. As"shaft 25 begins to assume the normal position shown in Fig. 4, thefollower spring 112 will urge the plunger cup 110 upwardly, which actionpermits the follower cup" 114 to begin to assume its normal position.The force which has been directing piston 93 to the left is reversed indirection, the flow of liquid thus being, reversed so that the liquid inthe area between piston cup 96' and plate 74'will move up passage andliquid will flow down passage 105 into the area between piston cup 96and plate 52. This action moves piston rod 90 to the right and allowsspring 89 to close valve 88, stopping the flow of additional air andmaintaining the original" position of the air spring. Spring 98 assistsin returning piston 93 to its normal position as equilibrium is beingreached.

If the static load on the vehicle suspension is'decreased, the framemembers 15 and 16 move upwardly away from the axle housing 18, causingthe air spring 12 to extend. During this upward movement'of the frame.members, the control device 10 also moves upwardly, causing shaft 25 tobe turned by rod 24, in a counterclockwise direction as viewed in Fig.4, said rod sliding with respect to the bolt 23 as the device 10 movesup.- wardly.

As the shaft 25is turned counter-clockwise on its From the latterpassage the liquid flows axis, the ensuing action is identical butopposite to that:

described in connection with Fig.5. That is, the folfitting 44, passage87, passage 63, chamber 162, orifice 101, passage 72, annular passage71, passage 1%, and the exhaust port 42 to the atmosphere. The exhaustof air from within the spring 12 will contract the air spring to itsinitial position.

As the air spring contracts, the frame members 15 and 16 move downwardlytoward the axle housing 18, causing shaft 25 to be turned by rod 24 inthe opposite or clockwise direction. The ensuing action at this point isalso identical but opposite to that described in connection with Fig. 5.That is, the force moving follower cup 114 is reversed in direction, andliquid will begin to flow from the area between piston cup 96 and plate5,210 the area between piston cup 95' and plate 74. Thisaction movespiston rod 92" toward bore 35 and allows the spring pressed valve 103 toclose, stopping the exhaust of air and maintaining the original positionof the airspring. The spring 93 assists in returning piston 93 to itsnormal position.

When a vehicle equipped with a suspension system according to thisinvention is driven over rough roads with no change in the staticloading, the vehicle wheels will move up and down over bumps and intoholes in the road. This causes the shaft 25 to be quickly turned ineither direction as the case may be. However, a quick turning of shaft25 wil not cause the various components of the control device to reactto supply or exhaust air because of the damping or time delay effect ofthe pistons 93-and 93' upon movementof the piston rods 90 and 90'. Thus,the admission of additional air to or exhaust of air from the air spring12 will not occur until a forceis maintained in one direction for apredetermined period of time which can be controlled by the needlevalves 108 and 108'. The use of two needle valves, one in connectionwith each piston, is a feature of this invention, which provides formore accurate selectivity of and more accurate control of the time lagrequired for damping the movement of the piston rods. Thus, valveopenings of different or the same sizes for this passage of liquidduring the dampingaction, may be easily and quickly prm vided. After theseveral springs in the device are balanced, it will be found desirableto choose needle valve openings which wil provide a time lag of about 7seconds before th follower cup 114 wil lmove from the normal or middleposition shown in Fig. 4, to either of its tilted positions, one ofwhich is shown in Fig. 5. However, the time delay may be selected fromany place within the preferred range of from 1 to 20 seconds.

A shut ofi valve (not shown) can be provided in the air spring line 33so that an operator can shut ofi the line when raising the vehicle by abumper jack to remove a tire.

While a preferred embodiment of the invention has been shown anddescribed, it will be understood that changes and modifications may bemade therein without departing from the spirit of the invention or thescope of the subjoined claims.

What is claimed is:

1. Control means adapted for regulation of the supply and exhaust of'air to and from an expansible bellows for a vehicle suspension systemto maintain a predetermined height between the road gear and frame ofthe vehicle, comprising, a housing, said housing having an air supplyport, an air exhaust port and a two-way port, with air passagewaysconnecting said supply port with said two-way port and said exhaust portwith said two-way port, opposed valves-'within said housing closing saidpassageways, opposed pistons located between said valves and movableftoopen said valves, that portion of the housing between said pistonshaving walls defining a bore at substantially a right angle to saidpistons, a shaft extending transversely of said.

bore adapted for rotation by relative movement between the road gear andframe of the vehicle, said shaft having a flattened surface, anoscillatable piston operating member including an outer member suspendedfrom said shaft, an inner cup in telescopic relation with said outermember and contacting said flattened surface, and a compressed followerspring within said inner cup urging the latter into contact with saidshaft, said operating member extending between said pistons so as toselectively actuate one of said pistons to open one of said valves.

in response to rotation of said shaft.

2.- Control means adapted for regulation of the supply and exhaust ofair to and from an expansible bellows for a vehicle suspension system tomaintain a predetermined height between the road gear and frame of thevehicle, comprising, a housing, said housing having an air supply port,an air exhaust port and a two-way port,

with air passageways connecting said supply port with said two-way portand said exhaust port with said two-way port, opposed valves within saidhousing closing said passageways, opposed pistons located between saidvalves and movable to open said valves, that portion of the housingbetween said pistons having walls defining a bore at substantially aright angle to said pistons, said housing further having passagewaystherethrough connecting the areas between said pistons and said valveswith said bore, a liquid completely filling said last named passageways,said areas and said bore, valves in said liquid filled passageways toregulate the size thereof, a shaft extending transversely of said boreadapted for rotation by relative movement between the road gear andframe of the vehicle, said shaft having a flattened surface, anoscillatable piston operating member including an outer member suspendedfrom'said shaft, an inner cup in telescopic relation with said outermember and contacting said flattened surface, and a compressed followerspring within said inner cup urging the latter into contact with saidshaft, said operating member extending between said pistons so as toselectively actuate one of said pistons t; ripen one of said valves inresponse to rotation of said s a t.

3. A control device for a vehicle pneumatic suspension system, saidsystem including an air spring containing a cushion of air interposedbetween the frame and road gear of said vehicle, comprising, a housingadapted for mounting remotely of said air spring, separate and opposedvalves in said housing for admitting air to and exhausting air from anair spring, a pair of opposed pistons located between said valves andindividually movable within said housing to selectively open saidvalves, each of said pistons including a resilient cup and a metalliccup holding the lip of said resilient .cup against the walls of saidhousing, said metallic cup having a corrugated portion extending beyondsaid resilient cup, a rotatable shaft mounted between said pistons, anoscillatable piston operating member operatively connected to said shaftto selectively actuate one of said pistons to open'one of said valvesupon rotation of said shaft, and damping means opposing the opening ofsaid one of said valves for a predetermined time after actuation of saidone of said pistons.

4. A control device according to claim 3 wherein said damping meansincludes passageways connecting the areas betweeen each associated valveand piston, a liquid completely filling said passageways and said areas,and valves in said passageways to selectively regulate the size thereof.

5. A control device for a vehicle pneumatic suspension system, saidsystem including an air spring containing a'cushion of airinterposed'between the frame and road gear of said vehicle, comprising,a housing adapted for mounting remotely of said air spring, separate andopposed valves in said housing for admitting air to and exhausting airfrom an air spring, a pair of opposed pistons located between saidvalves and individually movable within said housing to selectively opensaid valves, a rotatable shaft mounted between said pistons, anoscillatable piston operating member operatively connected to said shaftto selectively actuate one of said pistons to open one of said valvesupon rotation of said shaft, damping means opposing the opening of saidone of said valves for a predetermined time after actuation of said oneof said pistons, said shaft having a flattened surface, said pistonoperating member including an outer member suspended from said shaft, aninner cup telescoping within said outer member and contacting saidflattened surface of said shaft, and a spring interposed between saidinner cup and outer member and having a normal bias urging said innercup in a direction toward said shaft.

6. A control device for a vehicle pneumatic suspension systemcomprising, a housing, said housing having conduits therethrough for thepassage of air under pressure, opposed valves within said housingclosing said conduits, opposed pistons located between said valves andmovable within the housing to open said valves, each of said pistonsincluding a resilient cup and a metallic cup holding the lip of saidresilient cup against the walls of said housing, said metallic cuphaving a corrugated portion extending beyond said resilient cup, thatportion of the housing between said pistons having walls defining a boreat substantially a right angle to said pistons, a shaft extendingtransversely of said bore and exteriorly of said housing, oscillatorymeans within said bore responsive to movement of said shaft, saidoscillatory means extending between said pistons so as to selectivelyactuate said pistons to open said valves, and damping means opposing theopening of said valves for a predetermined time after actuation of saidpistons.

References Cited in the file of this patent UNITED STATES PATENTS1,371,648 Schmidt Mar. 15, 1921 2,670,201 Rossman Feb. 23, 19542,679,865 Grifiith June 1, 1954 2,753,891 Parker July 10, 1956 2,774,376Young Dec. 18, 1956

